Other pages

Ancient acoustical engineering

In SF#86/43*, we reviewed R. Waller's acoustical measurements
at ancient rock-art sites in Europe, North America, and Australia.
Waller claimed that some rock art was intentionally placed where
echos from the walls are not only exceptionally loud but are also
qualitatively related to the art's subject matter, such as running
hoofed animals.

The Newgrange chamber, with acoustical nodes and antinodes. Antinode occur at the chamber's stone walls.

In a similar venture, R.G. Jahn et al have taken sound generators
and meters into the chambers of six ancient structures and measured
their acoustical properties. The sites selected were: Wayland's
Smithy, Chun Quoit, and Cairn Euny, all in the U.K.; Newgrange,
and Cairns L and I, Carbane West, all in Ireland. All of these
sites date back to about 3,500 BC. The chambers were all bounded
by roughly hewn stones, but they had very different configurations.
Newgrange was cruciform (see sketch); others were rectangular,
beehive, and petalshaped. Quoting the abstract from the Princeton
report, here is what the acoustical surveys found:

"Rudimentary acoustical measurements performed inside six
diverse Neolithic and Iron Age structures revealed that each sustained
a strong resonance at a frequency between 95 and 120 Hz (wavelength
about 3m). Despite major differences in chamber shapes and sizes,
the resonant modal patterns all featured strong antinodes at the
outer walls, with appropriately configured nodes and antinodes
interspersed toward the central source. In some cases, internal
and exterior rock drawings resembled these acoustical patterns.
Since the resonant frequencies are well within the adult male
voice range, one may speculate that some forms of human chanting,
enhanced by the cavity resonance, were invoked for ritual purpose."